Ditto

The combination of Imposter and Choice Scarf allows Ditto to outspeed the foe, making it a strong setup deterrent and one of the best revenge killers to sweepers like Thundurus-T, Salamence, and Gyarados. Ditto also has utility against stall teams, as it cannot be easily PP stalled, especially if it is able to switch into Knock Off from Tangrowth, and can take advantage of transforming into opposing clerics like Umbreon and Chansey. However, Ditto can be awkward to fit onto teams, as it often cannot switch into anything safely or provide any defensive utility outside of Regenerator. Imposter also fails against Substitute, which can be problematic against sweepers like Primarina. Ditto is also unable to effectively stop bulkier setup sweepers with recovery such as Galarian Slowbro due to being Choice-locked.